Research


My ongoing research attempts to tackle various boundary layer turbulence and practical wind engineering problems using a combination of innovative approaches, such as state-of-the-art numerical simulations (large eddy simulations), novel analyses of field measurements, flow-visualizations and theoretical developments. Most of my research integrates ideas from a variety of disciplines such as micrometeorology, turbulence theory, computational fluid dynamics, and dynamical systems.  


Large Eddy Simulation (LES) of Atmospheric Boundary Layer Flows



Over the past few years, I have been actively involved in large eddy simulations of atmospheric boundary layers using a new generation subgrid-scale (SGS) scheme, named as the locally-averaged scale-dependent dynamic model. This SGS model, which does not require any parameter tuning, has shown noteworthy performance in simulating boundary layer flows (especially stably stratified flows) even at coarse resolutions. Details of this SGS modeling approach could be found in Basu et al. (2006) and Basu and Porte-Agel (2006). 


Currently, in my research, an array of advanced fast-response high-resolution monitoring systems (developed and assembled by the Texas Tech Atmospheric Science Group and the Wind Science and Engineering Center) is being utilized in conjunction with LES to improve our understanding of several intriguing boundary layer phenomena (e.g., low-level jet formation, intermittency in very stable boundary layer). The observational array consists of the West Texas Mesonet, a 200m tall instrumented tower, two boundary layer profilers and an upper-air sounding system. 




























Figure 2. Time-height plot of wind speed observed by the West Texas Mesonet wind profiler on May 25th, 2004. Low-level jet (LLJ) formation is clearly noticeable.  (Courtesy: Ian Giammanco, Texas Tech University)










Numerical weather prediction and climate models to a great extent rely on parameterizations of turbulent fluxes. Errors in these formulations can result in gross errors in boundary layer evolution and in turn could adversely affect the entire atmospheric circulation. One of the objectives of my ongoing research is to develop physically-based surface layer and boundary layer parameterizations for weather prediction models (e.g., WRF model). For this purpose, an extensive observational database (primarily collected by the West Texas Mesonet and 200m tower) is being effectively used. The West Texas Mesonet consists of more than 40 automated surface meteorological stations (10m tall towers) with an average spacing of 40km. Each station measures up to 15 meteorological and 10 agricultural parameters every 5 and 15 min, respectively. The 200m tall tower includes instrumented boom arms at 10 levels and continuously collects high-response turbulence variables.   







Figure 1. Vertical cross-section of  instantaneous potential temperature field obtained from a large eddy simulation of buoyancy-driven convective boundary layer.



Land-Atmosphere Interactions






Figure 3. Surface observations from the West Texas Mesonet (map created with WeatherScope)


























High-resolution turbulence measurements are also being used for dynamical and statistical characterizations of boundary layer turbulence (e.g., nonlinearity, predictability, multifractality). Apart from being of fundamental scientific interest, many of our findings might have significant impacts on the present-day turbulence modeling approaches [see Basu et al. (2004) for an example].



Figure 4. Fractal fern created by Iterative Function Systems (IFS). Similar idea was used by Basu et al. (2004) to synthetically generate turbulence signals.




 

















Dynamical Systems Approach to Turbulence